Landscape heterogeneity as a factor of bird communities diversity in northwest Croatia

Abstract

Struktura zajednica ptica uvelike je određena staništem te se mijenja s promjenama u okolišu. U mozaičnom poljoprivrednom staništu brdovitog dijela Hrvatske istraživane su značajke ptica i njihovog staništa. Ornitofauna je istraživana metodom brojanja u točki, a stanište je kartirano prema načinu korištenja. Ukupno je zabilježeno 50 vrsta ptica od čega je 39 obuhvaćeno kvantitativnom analizom. Na temelju udjela šume i ostale drvenaste vegetacije stanište je podijeljeno na četiri kategorije koje predstavljaju stupnjeve sukcesije. Ukupna gustoća ptica procijenjena je na 2162 para po km2, a najveća je u kategoriji III u kojoj je i raznolikost staništa najveća. Najbrojnija je vrsta kos Turdus merula, šumski generalist. Najviše ptica se gnijezdi u grmlju, a hrani na tlu. Šumske vrste dominiraju u svim kategorijama, a njihova je brojnost pozitivno korelirana s udjelom šume u staništu. S porastom udjela šume pada brojnost vrsta otvorenih staništa i ekotona, a smanjuje se i raznolikost ptica. Napredovanjem sukcesije i homogenizacijom staništa povećat će se broj šumskih vrsta, osobito generalista što će dodatno smanjiti raznolikost ptica.Bird community structure is determined by habitat and it changes along environment alterations. Research on avifaunal and habitat features was conducted in mosaic agricultural landscape in submontane part of Croatia. Birds were surveyed by point count method and habitat was classified into land-use types. In total, 50 bird species were recorded, of which 39 went through quantitative analyses. Habitat was divided into four categories by portion of forest and woody habitat types that correspond to different succession stages. Total estimated bird density was 2162 pairs per km2. Both bird and habitat densities were the highest in category III. The most numerous species was blackbird Turdus merula which is a forest generalist. Most birds nest in shrub and feed on ground. Forest birds were dominant group of species and tend to have higher abundance with larger portion of forest in habitat. Number of open-habitat birds and bird diversity was negatively correlated to proportion of forest. Number of forest species, especially generalists is expected to grow with more homogenous habitat and bird diversity will probably decrease